New study finds deep ocean microbes already prepared to tackle climate change

A research group co-led by the University of Illinois Urbana-Champaign predicts that a surprisingly adaptable species of marine archaea will play an important role in reshaping biodiversity in the planet’s oceans as the climate changes.
Photo Credit: Fred Zwicky

Scientific Frontline: Extended "At a Glance" Summary: Deep Ocean Ammonia-Oxidizing Archaea

The Core Concept: Nitrosopumilus maritimus is a highly adaptable species of marine archaea that accounts for approximately 30% of the marine microbial plankton population and plays a vital role in regulating the ocean's biological and chemical balance amid climate change.

Key Distinction/Mechanism: While it was previously thought that deep-ocean environments (1,000 meters or deeper) were insulated from surface warming, these iron-dependent microbes actively adapt to rising temperatures and decreased nutrient availability by lowering their iron requirements and significantly increasing their physiological iron-use efficiency.

Major Frameworks/Components: 

• Ammonia Oxidation: The metabolic process by which these archaea alter the forms of nitrogen available in seawater.
• Nutrient Cycling: The biogeochemical mechanism through which microbes control nitrogen and trace metal availability to sustain primary production.
• Iron-Use Efficiency: The physiological adaptation allowing marine microbes to survive and maintain chemical reactions under high-temperature and low-iron stress.
• Global Ocean Biogeochemical Modeling: The computational framework used to project how deep-ocean archaeal communities will maintain their ecological roles across iron-limited regions.

Branch of Science: Marine Microbiology, Global Change Biology, and Ocean Biogeochemistry.

Future Application: These laboratory findings and coupled biogeochemical models will be validated in real-world, open-ocean environments during upcoming maritime research expeditions. This will improve predictive models of how temperature and metal limitation interactive effects will reshape natural marine populations and global nutrient distribution.

Why It Matters: By driving essential chemical reactions and controlling the forms of nitrogen in seawater, these archaea regulate the growth of microbial plankton. Because microbial plankton form the base of the marine food chain, the adaptability of these archaea is critical to sustaining global marine biodiversity and oceanic health in a rapidly warming climate.

This summer, Qin will serve as co-chief scientist aboard the research vessel Sikuliaq. He and 20 other researchers will work to validate the study’s experimental findings in a real-world setting.
Photo Credit: Courtesy Wei Qin

Deep-sea waters are warming due to heat waves and climate change, and it could spell trouble for the oceans’ delicate chemical and biological balance. A new study, however, demonstrates that the microbe Nitrosopumilus maritimus may already be adapting well to warmer, nutrient-poor waters. Researchers predict that these surprisingly adaptable iron-dependent ammonia-oxidizing archaea will play an important role in reshaping ocean-nutrient distribution in a changing climate.

Nitrosopumilus maritimus and its kin account for approximately 30% of the marine microbial plankton population, and many researchers agree that the oceans depend on these microbes to drive the chemical reactions that support marine life. The ammonia-oxidizing activity of archaea makes them key players in the oceans’ nutrient cycling. By altering the forms of nitrogen available in seawater, they control the growth of microbial plankton — the base of the marine food chain — and help sustain marine biodiversity.

“Ocean-warming effects may extend to depths of 1,000 meters or more,” said University of Illinois Urbana-Champaign microbiology professor Wei Qin. “We used to think that deeper waters were mostly insulated from surface warming, but now it is becoming clear that deep-sea warming can change how these abundant archaea use iron — a metal they depend on heavily — potentially affecting trace metal availability in the deep ocean.”

Illinois microbiology professor Wei Qin.
Photo Credit: Fred Zwicky

The study, led by Qin and University of Southern California global change biology professor David Hutchins, used controlled, trace-metal-clean experiments to expose a pure culture of Nitrosopumilus maritimus to a variety of temperatures and iron concentrations. They observed that increasing the temperature under iron-limited conditions reduced the microbes’ iron requirements and increased physiological iron-use efficiency, demonstrating that the microbes acclimate well to the stress of higher temperatures and decreased iron availability.

“We coupled these findings with global ocean biogeochemical modeling by Alessandro Tagliabue from the University of Liverpool,” Qin said. “The results suggest that deep-ocean archaeal communities may maintain or even enhance their role in nitrogen cycling and primary production support across vast iron-limited regions in a warming climate.”

This summer, Qin will serve as co-chief scientist aboard the research vessel Sikuliaq. He and 20 other researchers will work to validate the study’s experimental findings in a real-world setting. Photo courtesy Wei Qin

This summer, Qin and Hutchins will serve as co-chief scientists aboard the research vessel Sikuliaq for a research expedition from Seattle to the Gulf of Alaska and then down to the subtropical gyre, stopping in Honolulu, Hawaii. Joining Qin will be 20 other researchers whose aim will be to validate the new experimental findings in a real-world setting and focus on the interactive effects of temperature and metal limitation on natural archaeal populations.

Additional information: Qin is also affiliated with the Carl R. Woese Institute for Genomic Biology.

Funding: The National Science Foundation, Simons Foundation, National Natural Science Foundation of China, University of Illinois Urbana-Champaign and the University of Oklahoma supported this research.

Published in journal: Proceedings of the National Academy of Sciences

Title: Ocean warming enhances iron use efficiencies of marine ammonia-oxidizing archaea

Authors: Wei Qin, Alessandro Tagliabue, Lei Hou, Min Xu, Xiaopeng Bian, Dawn M. Moran, Duo Zhao, Qian Li, Matthew R. McIlvin, Yue Zheng, Shuh-Ji Kao, Yao Zhang, Mak A. Saito, Seth G. John, Fei-Xue Fu, and David A. Hutchins

Source/Credit: University of Illinois Urbana-Champaign | Lois Yoksoulian

Reference Number: mcb030926_01

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